Electric drive units typically comprise an electric motor and a reduction drive arranged to reduce the rotational movement produced by the electric motor. The torque is transmitted from the reduction drive to a differential assembly which splits the torque onto two output shafts for driving wheels.
Electric or hybrid vehicles with an electric drive unit have long been known. Hybrid electric vehicles have a structure which combines two power sources, typically an internal combustion engine and an electric motor, to produce lower emissions. Hybrid electric drive units are being developed for use in all-wheel drive vehicles such that the motor and the engine can transmit power to both a front set of driven wheels and rear set of driven wheels.
In all-wheel drive hybrid electric vehicles, a reduction gear set reduces an output speed from an electric driving motor and transmits the reduced output speed to a differential gear assembly. The differential gear assembly distributes the introduced torque to two output shafts for driving the wheels so that one of the two output shafts can rotate at different rates with respect to one another. The differential gear assembly can automatically make a rotation difference when the rotation difference between left and right wheels on an axle is required, i.e. when a vehicle turns or moves on uneven road surfaces, leading to smooth driving.
Hybrid all-wheel drive systems present packaging difficulties for vehicle design. The integration of an electric drive or a hybrid drive with a downstream reduction gear set and differential gear assembly in a motor vehicle is often difficult and costly due to additional components required for the electric drive and the limited available space.